Apparatus for producing metal to be semimolten-molded

ABSTRACT

An improved apparatus for producing a semisolid shaping metal that has fine primary crystals dispersed in the liquid phase and which also has a uniform temperature distribution comprises a melt pouring section comprising a melting furnace which melts and holds a metal and a pouring device which lifts out the molten metal from said melting furnace, adjusts it to a specified temperature and pours it into a holding vessel, a nucleating section which generates crystal nuclei in the melt as it is supplied from said pouring device into said holding vessel, a crystal generating section which performs temperature adjustment such that the metal obtained from said nucleating section falls within a desired molding temperature range as it is cooled to a molding temperature at which it is partially solid, partially liquid, a holding vessel heating section which adjusts the temperature of the holding vessel when it is empty, a holding vessel conditioning section which inverts the holding vessel so that a partially molten metal is discharged and which then cleans the inner surfaces of the holding vessel, and a vessel transporting section furnished with an automating device including a robot with which the partially molten metal from said nucleating section is transported into the injection sleeve of a molding machine.

TECHNICAL FIELD

This invention relates to an apparatus for producing semisolid shapingmetals. More particularly, the invention relates to an apparatus withwhich semisolid metals suitable for semisolid shaping that have fineprimary crystals dispersed in the liquid phase and that have a uniformtemperature distribution can be produced in a very convenient and easyway.

BACKGROUND ART

A thixo-casting process is drawing researcher's attention these dayssince it involves a fewer molding defects and segregations, producesuniform metallographic structures and features longer mold lives butshorter molding cycles than the existing casting techniques. The billetsused in this molding method (A) are characterized by spheroidizedstructures obtained by either performing mechanical or electromagneticagitation in temperature ranges that produce semisolid metals or bytaking advantage of recrystallization of worked metals.

On the other hand, raw materials cast by the existing methods may alsobe molded in a semisolid state. There are three examples of thisapproach; the first two concern magnesium alloys that will easilyproduce an equiaxed microstructure and Zr is added to induce theformation of finer crystals [method (B)] or a carbonaceous refiner isadded for the same purpose [method (C)]; the third approach concernsaluminum alloys and a master alloy comprising an Al-5% Ti-1% B system isadded as a refiner in amounts ranging from 2-10 times the conventionalamount [method (D)]. The raw materials prepared by these methods areheated to temperature ranges that produce semisolid metals and theresulting primary crystals are spheroidized before molding.

It is also known that alloys within a solubility limit are heated fairlyrapidly up to a temperature near the solidus line and, thereafter, inorder to ensure a uniform temperature distribution through the rawmaterial while avoiding local melting, the alloy is slowly heated to anappropriate temperature beyond the solidus line so that the materialbecomes sufficiently soft to be molded [method (E)]. A method is alsoknown, in which molten aluminum at about 700° C. is cast to flow down aninclined cooling plate to form partially molten aluminum, which iscollected in a vessel [method (F)].

These methods in which billets are molded after they are heated totemperatures that produce semisolid metals are in sharp contrast with arheo-casting process (G), in which molten metals containing sphericalprimary crystals are produced continuously and molded as such withoutbeing solidified to billets. It is also known to form a rheo-castingslurry by a method in which a metal which is at least partially solid,partially liquid and which is obtained by bringing a molten metal intocontact with a chiller and inclined chiller is held in a temperaturerange that produces a semisolid metal [method (H)].

Further, a casting apparatus (I) is known which produces a partiallysolidified billet by cooling a metal in a billet case either from theoutside of a vessel or with ultrasonic vibrations being applied directlyto the interior of the vessel and the billet is taken out of the caseand shaped either as such or after reheating with r-f induction heater.

However, the above-described conventional methods have their ownproblems. Method (A) is cumbersome and the production cost is highirrespective of whether the agitation or recrystallization technique isutilized. When applied to magnesium alloys, method (B) is economicallydisadvantageous since Zr is an expensive element and speaking of method(C), in order to ensure that carbonaceous refiners will exhibit theirfunction to the fullest extent, the addition of Be as an oxidationcontrol element has to be reduced to a level as low as about 7 ppm butthen the alloy is prone to burn by oxidation during the heat treatmentjust prior to molding and this is inconvenient in operations.

In the case of aluminum alloys, about 500 μm is the crystal grain sizethat can be achieved by the mere addition of refiners and it is not easyto obtain crystal grains finer than 200 μm. To solve this problem,increased amounts of refiners are added in method (D) but this isindustrially difficult to implement because the added refiners are proneto settle on the bottom of the furnace; furthermore, the method iscostly. Method (E) is a thixo-casting process which is characterized byheating the raw material slowly after the temperature has exceeded thesolidus line such that the raw material is uniformly heated andspheroidized. In fact, however, an ordinary dendritic microstructurewill not transform to a thixotropic structure (in which the primarydendrites have been spheroidized) upon heating. According to method (F),partially molten aluminum having spherical particles in themicrostructure can be obtained conveniently but no conditions areavailable that provide for direct shaping. What is more, thixo-castingmethods (A)-(F) have a common problem in that they are more costly thanthe existing casting methods because in order to perform molding in thesemisolid state, the liquid phase must first be solidified to prepare abillet, which is heated again to a temperature range that produces asemisolid metal. In addition, the billets as the starting material aredifficult to recycle and the fraction liquid cannot be increased to avery high level because of handling considerations.

In contrast, method (G) which continuously generates and supplies amolten metal containing spherical primary crystals is more advantageousthan the thixo-casting approach from the viewpoint of cost and energybut, on the other hand, the machine to be installed for producing ametal material consisting of a spherical structure and a liquid phaserequires cumbersome procedures to assure effective operative associationwith the casting machine to yield the final product. Specifically, ifthe casting machine fails, difficulty arises in the processing of thesemisolid metal.

Method (H) which holds the chilled metal for a specified time in atemperature range that produces a semisolid metal has the followingproblem. Unlike the thixo-casting approach which is characterized bysolidification into billets, reheating and subsequent shaping, themethod (H) involves direct shaping of the semisolid metal obtained byholding in the specified temperature range for a specified time and inorder to realize industrial continuous operations, it is necessary thatan alloy having a good enough temperature distribution to establish aspecified fraction liquid suitable for shaping should be formed within ashort time. However, the desired rheo-casting semisolid metal which hasspherical primary crystals, a fraction liquid and a temperaturedistribution that are suitable for shaping cannot be obtained by merelyholding the cooled metal in the specified temperature range for aspecified period. Too rapid cooling will deteriorate the temperaturedistribution. In addition, if the cooling means is contacted by themelt, a solidified metal will remain either on the cooling means orwithin the holding vessel, making it impossible to perform continuousoperation.

In method (I), a case for cooling the metal in a vessel is employed butthe top and the bottom portions of the metal in the vessel will coolfaster than the center and it is difficult to produce a partiallysolidified billet having a uniform temperature distribution andimmediate shaping will yield a product of nonuniform structure. What ismore, considering the need to satisfy the requirement that the partiallysolidified billets as taken out of the billet case have such atemperature that the initial state of the billet is maintained, it isdifficult for the fraction liquid of the partially solidified billet toexceed 50% and the maximum that can be attained practically is no morethan about 40%, which makes it necessary to give special considerationsin determining injection and other conditions for shaping by diecasting.If the fraction liquid of the billet has dropped below 40%, it could bereheated with a r-f induction heater but it is still difficult to attaina fraction liquid in excess of 50% and special considerations must bemade in injection and other shaping conditions. In addition, eliminatingany significant temperature uneveness that has occurred within thepartially solidified billet is a time-consuming practice and it isrequired, although for only a short time, that the r-f induction heaterproduces a high power comparable to that required in thixo-casting. Inaddition it is necessary to install multiple units of the r-f inductionheater in order to achieve continuous operation in short cycles.

Another problem with the industrial practice of shaping semisolid metalsin a continuous manner is that if a trouble occurs in the castingmachine, the semisolid metal may occasionally be held in a specifiedtemperature range for a period longer than the prescribed time. Unless acertain problem occurs in the metallographic structure, it is desiredthat the semisolid metal be maintained at a specified temperature; inpractice, however, particularly in the thixo-casting process where thesemisolid metal is held with its temperature elevated from roomtemperature, the metallographic structure becomes coarse and the billetsare considerably deformed (progressively increase in diameter toward thebottom). In addition, unless their temperatures are individuallycontrolled, such billets are usually discarded and cannot be used asthixo-billets.

The present invention has been accomplished under these circumstances ofthe prior art and its principal object is to provide an apparatus thatdoes not require to use billets or any cumbersome procedures but whichensures that semisolid metals (including those which have higher valuesof fraction liquid than what are obtained by the conventionalthixo-casting process) which are suitable for subsequent shaping onaccount of both a uniform structure containing spheroidized primarycrystals and uniform temperature distribution can be produced in aconvenient, easy cost-effective way. In addition, if the need arises tocontrol the semisolid metal by holding it at a specified temperatureduring prolonged machine trouble or in the case where a semisolid metalhaving a specified fraction liquid is rapidly produced to permit highshot-cycle operations and where it is adjusted to fall within aspecified temperature range prior to molding, the apparatus is capableof producing a semisolid metal suitable for semisolid shaping by holdingthe metal's temperature uniformly at a constant level with such greatrapidity that the power requirement of the r-f induction heater is nomore than 50% of what is commonly spent in shaping by the thixo-castingprocess.

DISCLOSURE OF INVENTION

The stated object of the invention can be attained by the apparatus of afirst embodiment of present invention for producing a semisolid shapingmetal that has fine primary crystals dispersed in the liquid phase andwhich also has a uniform temperature distribution, said apparatuscomprising a melt pouring section comprising a melting furnace whichmelts and holds a metal and a pouring device which lifts out the moltenmetal from said melting furnace, adjusts it to a specified temperatureand pours it in a holding vessel, a nucleating section which generatescrystal nuclei in the melt as it is supplied from said pouring deviceinto said holding vessel, a crystal generating section which performstemperature adjustment such that the metal obtained from said nucleatingsection falls within a desired molding temperature range as it is cooledto a molding temperature at which it is partially solid, partiallyliquid, a holding vessel conditioning section which inverts the holdingvessel by turning it upside down so that a partially molten metal isdischarged and which then cleans the inner surfaces of the holdingvessel, and a vessel transporting section furnished with an automatingdevice including a robot with which the partially molten metal from saidnucleating section is transported into the injection sleeve of a moldingmachine.

According to a second embodiment of the present invention, the meltpouring section of the apparatus of the first embodiment of the presentinvention comprises, (1) a high-temperature melt holding furnace and alow-temperature melt holding furnace furnished with a pouring ladle, or(2) a pouring ladle furnished with a refiner feed unit and a temperaturecontrol cooling jig inserting device and a high-temperature melt holdingfurnace, or (3) a low-temperature melt holding furnace furnished with apouring ladle and a refiner-rich melt holding furnace also furnishedwith a pouring ladle, (4) a pouring ladle furnished with a refinermelting radio-frequency induction heater and a low-temperature meltholding vessel, or (5) a low-temperature melt holding vessel furnishedwith a pouring ladle, and wherein the nucleating section is the holdingvessel.

According to a third embodiment of the present invention which is asubembodiment of the second embodiment of present invention, thenucleating means comprises either a holding vessel tilting or invertingunit by which the angle of inclination of the holding vessel can bevaried freely and automatically as required during and after pouring ofthe melt in accordance with its volume, or a holding vessel coolingaccelerating unit capable of cooling said holding vessel externallyduring and after pouring of the melt, or both of said holding vesseltilting or inverting unit and said holding vessel cooling acceleratingunit.

According to a fourth embodiment of the present invention which is asubembodiment of the first, the melt pouring means is a low-temperaturemelt pouring furnace furnished with a pouring ladle and the nucleatingmeans comprises a vibrating jig and the holding vessel, said vibratingjig imparting vibrations to the melt as it is poured into said holdingvessel which is capable of vertical movement.

According to a fifth embodiment of the present invention which isanother subembodiment of the first embodiment of the present invention,the melt pouring means is a melt holding furnace furnished with apouring ladle and the nucleating means comprises an inclining coolingjig and the holding vessel, said cooling jig being such that the angleof inclination can be varied freely and automatically during and afterpouring of the melt in accordance with its volume.

According to a sixth embodiment of the present invention which is yetanother subembodiment of the embodiment of the present invention, thecrystal generating means comprises a vertically movable frame on whichthe holding vessel is placed and which is either furnished with a sourcefor heating the bottom portion of said holding vessel or formed of aninsulating material for heat-retaining said bottom portion, a verticallymovable lid that is either furnished with a heating source for heatingthe top portion of said holding vessel or formed of an insulatingmaterial for heat-retaining said top portion and which is furnished witha temperature sensor for measuring the temperature of the melt in theholding vessel, and a cooling unit provided exterior to said holdingvessel for injecting air of a specified temperature against the outersurface of said holding vessel.

According to a seventh embodiment of the present invention which is asubembodiment of the six embodiment, the crystal generating meanscomprises an induction apparatus furnished with a heating coil which isprovided around the holding vessel for controlling the temperature ofthe metal in the holding vessel, a frame that is capable ofheat-retaining or heating the bottom portion of the holding vessel andwhich is vertically movable for retaining or lifting out said holdingvessel and for adjusting its position within the heating coil of theinduction apparatus, a vertically movable lid that is capable ofheat-retaining or heating the top portion of said holding vessel andwhich is furnished with a temperature sensor for measuring thetemperature of the metal in the holding vessel, and a cooling unitprovided exterior to said heating coil for injecting air of a specifiedtemperature against the outer surface of said holding vessel.

According to an eighth embodiment of the present invention which isanother subembodiment of the sixth embodiment, the crystal generatingmeans comprises an induction apparatus furnished with a heating coilwhich is provided around the holding vessel for controlling thetemperature of the metal in the holding vessel, a frame that is capableof heat-retaining or heating the bottom portion of the holding vesseland which is not only vertically movable but also rotatable forretaining, lifting out or replacing said holding vessel and foradjusting its position within the heating coil of the inductionapparatus, a vertically movable lid that is capable of heat-retaining orheating the top portion of said holding vessel and which is furnishedwith a temperature sensor for measuring the temperature of the metal inthe holding vessel, and a cooling unit provided exterior to said heatingcoil for injecting air of a specified temperature against the outersurface of said holding vessel. The crystal generating means comprises aplurality of units which rotate or pivot about a single axis.

According to a ninth embodiment which is yet another subembodiment ofthe sixth embodiment of the present invention, the crystal generatingmeans comprises a frame that is capable of heat-retaining or heating thebottom portion of the holding vessel, a vertically movable lid that iscapable of heat-retaining or heating the top portion of said holdingvessel and which is furnished with a temperature sensor for measuringthe temperature of the metal in the holding vessel, a cooling zonecomprising a cooling unit which injects air or water of a specifiedtemperature, as required, against the outer surface of said holdingvessel, and a temperature adjusting zone having an induction apparatusfurnished with a heating coil which is provided around said holdingvessel for controlling the temperature of the metal in said holdingvessel.

According to a tenth embodiment of the present invention which is, thecrystal generating means further includes an automatic transport unitwith which the holding vessel containing the metal cooled to a specifiedtemperature in the cooling zone is moved at a specified speed to thetemperature adjusting zone which is adapted to be such that either theheating coil of the induction apparatus or the holding vessel moves sothat the temperature of the metal in the holding vessel is controlledwithin the heating coil.

According to an eleventh embodiment of the present invention which isanother subembodiment of the ninth embodiment of the present invention,the crystal generating means further includes a transport unitcomprising an automating device including a robot with which the holdingvessel containing the metal cooled to a specified temperature in thecooling zone is moved to the temperature adjusting zone which is adaptedto be such that either the heating coil of the induction apparatus orthe holding vessel moves so that the temperature of the metal in theholding vessel is controlled within the heating coil.

According to a twelfth embodiment of the present invention which is anembodiment of an embodiment of first of the present invention, theholding vessel conditioning means comprises at least two of thefollowing three units, i.e., a holding vessel cooling unit that iscapable of rotary and vertical movements and which is also capable ofinjecting at least one of a gas, a liquid and a solid material, an airblowing unit that is capable of rotary and vertical movements andoptional air injection, and a cleaning unit for cleaning the innersurfaces of the holding vessel which has a brush that is capable ofrotary and vertical movements and air injection, as well as a spray unitthat is capable of rotary and vertical movements and application of anonmetallic coating, and a holding vessel rotating and transporting unitwith which the holding vessel, with its opening facing down, can bemoved to and fixed on the top portion of each of said cooling unit, saidair blowing unit and said cleaning unit, and which is verticallymovable.

According to a thirteenth embodiment of the present invention which isanother subembodiment of the first embodiment of the present invention,the holding vessel conditioning means comprises a cleaning unit and aspray unit, said cleaning unit comprising a jig for cleaning the innersurfaces of the holding vessel which has a brush that is capable ofrotary and vertical movements and air injection and a vertically movablejig for fixing the holding vessel, and said spray unit comprising avertically movable jig for applying a nonmetallic coating onto the innersurfaces of the holding vessel and a vertically movable jig for fixingthe holding vessel.

According to fourteenth embodiment of the present invention which is yetanother subembodiment of the first embodiment of the present invention,the temperature of the holding vessel is adjusted when it is empty.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the general layout of the apparatus of theinvention for producing a semisolid shaping metal.

FIG. 2 is a side view of a cleaning unit in the holding vesselconditioning section of the invention apparatus.

FIG. 3 is a vertical section showing enlarged the essential componentsof the cleaning unit.

FIG. 4 is a vertical section of the holding vessel heating section ofthe invention apparatus.

FIGS. 5a, 5b, 5c, 5d and 5e are schematics which the step of generatingnuclei in the crystal generating section of the invention apparatus bylow-temperature melt pouring techniques.

FIG. 6 illustrates the step of generating nuclei in the crystalgenerating section of the invention apparatus by a vibration technique.

FIG. 7a, 7b and 7c are schematics which illustrate the step ofgenerating nuclei in the crystal generating section of the inventionapparatus by contact with a cooling plate.

FIG. 8 is a vertical section of the crystal generating section of theinvention apparatus.

FIG. 9 is a flowsheet illustrating the process for producing a semisolidshaping metal using the apparatus of the invention.

FIG. 10 is a cycle chart for the continuous semisolid shaping operationusing the invention apparatus.

FIG. 11 is a diagrammatic representation of a micrograph showing themetallographic structure of a shaped part from the shaping metalproduced by the invention.

FIG. 12 is a plan view showing the general layout of an apparatus forproducing a semisolid shaping metal which comprises a crystal generatingmeans and a holding vessel conditioning means which have rotatingcapabilities according to the invention.

FIG. 13a is a plan view showing details of the crystal generating meansshown in FIG. 12. FIG. 13b is vertical section A--A of FIG. 13a.

FIG. 14 is a side view of the rotating and transporting unit and thecleaning unit in the holding vessel conditioning means of the invention.

FIG. 15 is a side view of a holding vessel tilting or inverting deviceaccording to the invention.

FIG. 16 is a plan view showing the general layout of an apparatus forproducing a semisolid shaping metal which has a crystal generating meanscomprising a cooling zone and a temperature adjusting zone according tothe invention.

FIG. 17a is a plan view showing details of the crystal generating meansshown in FIG. 16.

FIG. 17b is vertical section B--B of FIG. 17a.

FIG. 18 is a plan view showing the general layout of an apparatus forproducing a semisolid shaping metal which has a stationary crystalgenerating means comprising a cooling zone and a temperature adjustingzone according to the invention.

FIG. 19a is a plan view showing details of the crystal generating meansshown in FIG. 18.

FIG. 19b is vertical section C--C of FIG. 19a.

BEST MODE FOR CARRYING OUT THE INVENTION

In the present invention, a metal melted in a melting furnace is treatedby either one of the following methods to generate crystal nuclei withinthe melt: it is directly poured into a holding vessel as alow-temperature melt that contains a specified refiner and which is heldsuperheated to less than 50° C. above the liquidus temperature of themetal; it is poured into the holding vessel as a low-temperature meltthat is held superheated to less than 50° C. above the liquidustemperature of the metal with vibrations being applied to the melt inthe holding vessel as it is poured into the latter; or the melt ispoured into the holding vessel as it is brought into contact with acooling plate that can be inclined at varying angles. The melt havingcrystal nuclei generated therein in the crystal generating section iscooled to a temperature where a specified fraction liquid isestablished, with the top or bottom of the holding vessel beingheat-retained or heated and with optional r-f induction heating, so thata semisolid shaping metal having a uniform temperature distribution andfine non-dendritic (spherical) primary crystals is produced not laterthan the start of shaping; the holding vessel is then transported bymeans of a robot into the injection sleeve of a molding machine such asa die-casting machine for subsequent shaping.

Examples of the invention will now be described in detail with referenceto accompanying drawings FIGS. 1-19, in which: FIG. 1 is a plan viewshowing the general layout of an apparatus for producing a semisolidshaping metal; FIG. 2 is a side view of a cleaning unit in the holdingvessel conditioning section of the apparatus; FIG. 3 is a verticalsection showing enlarged the essential components of the cleaning unit;FIG. 4 is a vertical section of the holding vessel heating section ofthe apparatus; FIGS. 5a-5e illustrate the step of generating nuclei inthe crystal generating section of the apparatus by low-temperature meltpouring techniques; FIG. 6 illustrates the step of generating nuclei inthe crystal generating section by a vibration technique; which FIGS.7a-c illustrate the step of generating nuclei in the crystal generatingsection by contact with a cooling plate; FIG. 8 is a vertical section ofthe crystal generating section; FIG. 9 is a flowsheet illustrating theprocess for producing a semisolid shaping metal; FIG. 10 is a cyclechart for the continuous semisolid shaping operation; FIG. 11 is adiagrammatic representation of a micrograph showing the metallographicstructure of a shaped part obtained from the shaping metal produced bythe invention; FIG. 12 is a plan view showing the general layout of anapparatus for producing a semisolid shaping metal which comprises acrystal generating means and a holding vessel conditioning means whichhave rotating capabilities; FIG. 13a is a plan view showing details ofthe crystal generating means shown in FIG. 12; FIG. 13b is verticalsection A--A of FIG. 13a; FIG. 14 is a side view of the rotating andtransporting unit and the cleaning unit in the holding vesselconditioning means; FIG. 15 is a side view of a holding vessel tiltingor inverting device; FIG. 16 is a plan view showing the general layoutof an apparatus for producing a semisolid shaping metal which has acrystal generating means comprising a cooling zone and a temperatureadjusting zone; FIG. 17a is a plan view showing details of the crystalgenerating means shown in FIG. 16; FIG. 17b is vertical section B--B ofFIG. 17a; FIG. 18 is a plan view showing the general layout of anapparatus for producing a semisolid shaping metal which has a stationarycrystal generating means comprising a cooling zone and a temperatureadjusting zone; FIG. 19a is a plan view showing details of the crystalgenerating means shown in FIG. 18; and FIG. 19b is vertical section C--Cof FIG. 19a.

As FIG. 1 shows, the apparatus of the invention for producing semisolidshaping metals which is generally indicated by 100 comprises the holdingvessel conditioning section 10, the holding vessel heating section 20,the crystal generating section 30, a melt pouring section 40, anucleating section 50 and a vessel transporting section 60. A moldingmachine 200 is an example of the machines for shaping a semisolid metalM_(B) produced by the invention apparatus 100.

As also shown in FIG. 1, the holding vessel conditioning section 10comprises a cleaning unit 12 and a spray unit 14. As shown specificallyin FIG. 2, the cleaning unit 12 is comprised of a vertically movablecylinder 12a, a motor 12b mounted at the distal end of the piston rod onthe cylinder 12a and a brush 12c which is pushed into the holding vessel1 by means of the motor 12b and rotates to inject air. After the end ofmelt pouring, a robot 62 in the vessel transporting section 60 whichwill be described later transports the holding vessel 1 into aninjection sleeve 202a; the vessel is replaced upside down on a receivingstage 13 and a holding vessel retainer 13a provided just above thereceiveing stage 13 is lowered gently by means of a vertically movingcylinder 13b, so that the bottom of the vessel 1 is lightly presseddownward until it is secured to the receiving stage.

Thereafter, the brush 12c going up into the vessel 1 is driven to rotateso that all of its inner surfaces including the bottom and lateral sideare cleaned to dislodge the residual metal deposit on those surfaces. Asshown, a closing cover 12d is provided downward around the receivingstage 13 and the dropping metal deposit is collected by a receiving tray12e.

After the cleaning operation, the brush 12c is retracted downward andthe receiving stage 13 and vessel retainer 13a, with the holding vessel1 retained therebetween, and the vertically moving cylinder 13b make alateral shift in unison from the cleaning position to the spray position(the position of the spray unit 14 indicated in FIG. 1) by means of ashift cylinder indicated by 15 in FIG. 1. As shown specifically in FIG.3, the spray unit 14 comprises a vertically movable cylinder 14a, a pipe14b fitted at the distal end of the piston rod on the cylinder 14a and aspray nozzle 14c at the distal end of the pipe 14b. A water-solublecoating containing a nonmetallic substance and air are injected throughthe nozzle 14c for a specified time so that all inner surfaces of theholding vessel 1 including the bottom and lateral side are sprayed withthe coating; the applied coating is dried with air to make the innersurfaces of the holding vessel 1 cleaner.

The cleaning unit 12 and the spray unit 14 may be operated in every shotor they may be activated at regular intervals consisting of severalshots. Any nonmagnetic substance that deposited on the inner surfaces ofthe holding vessel and which has been removed in the cleaning operationsis recovered from the receiveing tray 12e at regular intervals of time.The spraying operation is for avoiding direct contact between the innersurfaces of the holding vessel 1 and the molten metal being poured intoit and must be performed if it is made of a metal. The coating to beapplied is selected from the group consisting of graphite-based moldreleases, non-graphite-based mold releases (containing talc, mica, etc.)and BN.

As shown specifically in FIG. 4, the holding vessel heating section 20comprises a cylinder frame 21, a vertically movable cylinder 22extending up and down through the frame 21 for use in heating theholding vessel 1, support frame 23 that can be moved up and down bymeans of the cylinder 22, a ceramic frame 24 fixed on the support frame23 for use in heating the holding vessel 1 and a heating furnace 25 forheating the holding vessel 1 placed on the frame 24.

After cleaning and spraying with the cleaning unit 12 and the spray unit14, respectively, in the holding vessel conditioning section 10, theholding vessel 1 is picked up by the robot 62 and replaced on the frame24, which then is moved up by means of the cylinder 22. When the supportframe 23 and the frame 24 have ascended to the positions indicated inFIG. 4, the holding vessel 1 will enter the heating furnace 25, which isthen closed off. The heating furnace 25 may have an internal heater or,alternatively, a hot blast may be blown from the outside.

After a specified time, the holding vessel 1 on the frame 24 which hasbeen heated to a specified temperature (say, 200° C.) is taken out ofthe furnace by the descent of the cylinder 22. The heated holding vessel1 is picked up by the robot 62 and transferred to the melt pouringsection 40, where it is charged with a melt and thereafter transferredto the nucleating section 50. The "holding vessel" as used in theinvention is a metallic or nonmetallic vessel (including a ceramicvessel), or a metallic vessel having a surface coated with nonmetalicmaterials, or a metallic vessel composited with nonmetallic materials.The wall thickness of the holding vessel 1 should be such that nosolidified layer will form on the inner surfaces of the vesselimmediately after pouring the melt or that even if a solidified layerforms, it will easily remelt upon heating with an induction heater 31 tobe described later.

Each of the melt pouring section 40 and the nucleating section 50 isconstructed differently depending upon the method of generating crystalnuclei. FIGS. 5a-5d are side views of the melt pouring section 40 andthe nucleating section 50 for the case where nucleation is effected bypouring a low-temperature melt in the presence of a refiner.

FIG. 5a shows the case where the melt pouring section 40 consists of ahigh-temperature melt holding furnace 41 and a low-temperature meltholding furnace 42 which is furnished with a pouring ladle 42a. Thehigh-temperature melt holding furnace 41 holds a high-temperature moltenmetal M₁ which has a high-melting refiner (Al--Ti--B alloy) N dissolvedtherein and which is held at 650° C. or above, preferably at 680° C. orabove. The molten metal M₁ is poured from the high-temperature meltholding furnace 41 into the low-temperature melt holding furnace 42,where it is held at a lower temperature such that it is superheated tono more than 50° C. above the liquidus temperature of the metal. Theresulting low-temperature melt M₂ is poured into the holding vessel 1(i.e., the nucleating section 50) by means of the ladle 42a, whereuponcrystal nuclei form in the melt. If Ti is the sole refiner in the melt,it is held superheated to no more than 30° C. above the liquidustemperature of the metal. In the case of a magnesium alloy containingboth Sr and Si or containing Ca alone, the degree of superheating shouldbe no more than 25° C. If this upper limit is exceeded, fine sphericalprimary crystals will not form.

FIG. 5b shows the case where the melt pouring section 40 consists of apouring ladle 42a furnished with a refiner feed unit 43 and atemperature control cooling jig inserting device 51 and ahigh-temperature melt holding furnace 41. A high-temperature moltenmetal M₃ which has a refiner N (containing Ti) dissolved therein andwhich has been held at 650° C. or above, preferably at 680° C. or above,in the high-temperature melt holding furnace 41 is lifted out with theladle 42a and supplied with an additional refiner (Al--Ti--B alloy) Nfrom the refiner feed unit 43. Thereafter, a cooling jig 51a on thedevice 51 is submerged into the melt in the ladle 42a so that it iscooled to such a temperature that it is superheated to no more than 50°C. above the liquidus temperature of the metal. This yields alow-temperature molten metal. In order to prevent the formation of asolidified layer, the melt must be vibrated as the cooling jig 51a issubmerged. However, if the temperature of the molten metal in theholding vessel 1 is such that it is superheated to at least 10° C. abovethe liquidus temperature of the metal, one cannot expect nuclei to begenerated by vibrations. Therefore, the low-temperature melt M₂ in theladle 42a is poured into the holding vessel 1 (i.e., the nucleatingsection 50), whereupon crystal nuclei are generated.

FIG. 5c shows the case where the melt pouring section 40 consists of alow-melt holding furnace 42 furnished with a pouring ladle 42a andanother low-temperature melt holding furnace 42 which is also furnishedwith a pouring ladle 42a and which is capable of holding a melt rich ina refiner Al--Ti--B alloy. A Ti-containing low-temperature melt M whichis lifted out of the low-temperature melt holding furnace 42 by means ofthe ladle 42a is mixed and diluted with a low-temperature melt of highTi and B contents M₄ that is lifted out of the other low-temperaturemelt holding furnace 42 by means of the ladle 42a. The low-temperaturemelt M₂ in the ladle 42a is poured into the holding vessel 1 (i.e., thenucleating section 50), whereupon crystal nuclei are generated.

FIG. 5d shows the case where the melt pouring section 40 consists of apouring ladle 42a furnished with a refiner melting r-f induction heater44 and a low-temperature melt holding furnace 42. A Ti-containinglow-temperature molten metal M₅ is lifted out of the low-temperaturemelt holding furnace 42 by means of the ladle 42a, into which a refiner(Al--Ti--B alloy) N is charged after being melted by means of a r-finduction coil 44a. The low-temperature melt M₂ in the ladle 42a ispoured into the holding vessel 1 (i.e., the nucleating section 50),whereupon crystal nuclei are generated.

FIG. 5e shows the case where the melt pouring section 40 consists of apouring ladle 42a and a low-temperature melt holding furnace 42. Alow-temperature molten metal M₆ near the melting point in the holdingladle 42a is poured into the holding vessel 1 (i.e., the nucleatingsection 50), whereupon crystal nuclei are generated. If Ti is the solerefiner in the melt, it is held superheated to no more than 30° C. abovethe liquidus temperature of the metal.

FIG. 6 is a side view of the melt pouring section 40 and the nucleatingsection 50 for the case of generating nuclei by applying vibrations. Themelt pouring section 40 consists of the low-temperature melt holdingfurnace 42 furnished with the pouring ladle 42a, a submergible vibratingjig 52 that can be moved up and down by means of a vertically movingcylinder 52a, and a jig 53 for vibrating the holding vessel 1. Togenerate crystal nuclei in the Ti-containing low-temperature moltenmetal M₅ being poured into the holding vessel 1 from the ladle 42a,vibrations are applied by the following two methods: submerging thevibrating jig 52 into the surface of the melt M₅ and placing thevibrating jig 53 into contact with the outer surface of the holdingvessel 1. It should be mentioned that crystal nuclei can be generatedeven if no refiners are contained in the melt being poured into theholding vessel 1. In order to ensure that there will be no uneventemperature distribution about it, the submerged vibrating jig 52 shouldbe disengaged from the surface of the melt as soon as the pouring stephas ended. The term "vibration" as used herein is in no way limited interms of the type of the vibrator used and the vibrating conditions(frequency and amplitude) and any commercial pneumatic and electricvibrators may be employed. As for the applicable vibrating conditions,the frequency typically ranges from 10 Hz to 50 kHz, preferably from 50Hz to 1 kHz, and the amplitude ranges from 1 mm to 0.1 μm, preferablyfrom 500 μm to 10 μm, per side.

FIG. 7 is a side view of the melt pouring section 40 and the nucleatingsection 50 for the case of generating nuclei by contact with a coolingplate. The melt pouring section 40 consists of a melt holding furnaceassembly 40A (comprising a high-temperature melt holding furnace 41 anda low-temperature melt holding furnace 42) furnished with a pouringladle 42a. The temperature of the melt in the melt holding furnaceassembly 40A is not limited to any particular value; however, if itstemperature is unduly high, it will become superheated to at least 10°C. above the liquidus temperature of the metal after it has passed overan inclining cooling jig 70 and no crystal nuclei will be formed.Therefore, the melt in the holding furnace assembly 40A is preferablysuperheated to no more than 50° C. above the liquidus temperature of themetal. The nucleating section 50 consists of the inclining cooling jig70 and the holding vessel 1. The cooling jig 70 has a water tank 71 thatis freely and automatically adjustable during and after pouring of themelt in accordance with the angle of inclination of the jig 70 and thepour volume of the melt. As the volume of the molten metal that ispoured from the ladle 42a into the holding vessel 1 while making contactwith the inclined cooling jig 70 approaches the upper limit, the angleof inclination of the jig 70 is reduced by means of a vertically movablecylinder 72. After the end of the pouring of the melt, the cooling jig70 is inclined in opposite direction so that the metal deposit on thesurface of the jig 70 drops into a metal deposit recovery tank 73.

In the cases described above, the melt pouring section 40 uses thepouring ladle 42 but this may be replaced by a pouring pump.

FIG. 8 shows the details of the crystal generating section 30. As shown,it comprises an induction heater 31 furnished with a heating coil 31awhich is provided around the holding vessel 1 for controlling thetemperature of the metal in it, a vertically movable cylinder 32, asupport frame 33 that can be moved up and down by means of the cylinder32 for retaining or lifting out the holding vessel 1 and for adjustingits position within the heating coil 31a, ceramic frame 34 placed on thesupport frame 33, a ceramic lid 35 capable of heat-retaining or heatingthe top of the holding vessel 1 and which is furnished with athermocouple 36 for measuring the temperature of the metal in theholding vessel 1, a cooling unit 37 which is provided exterior to theheating coil 31a for injecting air of a specified temperature againstthe outer surface of the holding vessel 1, and a protective cover 38surrounding the induction heater 31, frame 34, lid 35 and cooling unit37.

The induction heater 31 is effective for providing a uniform temperaturedistribution and ensuring a constant temperature after the temperatureof the metal in the holding vessel has been lowered rapidly or when atrouble occurs to the molding machine 200. If it is necessary to coolthe metal faster than when it is cooled with air, the cooling unit whichinjects air may be replaced by a device which sprays the holding vessel1 with water before it ascends to the position where the inductionheater 31 is provided.

After being charged with the molten metal M_(A) into which crystalnuclei have been introduced in the nucleating section 50, the holdingvessel 1 is picked up by the robot 62 and replaced on the ceramic frame34, which then is moved up by means of the cylinder 32 until it stops ata specified position in the induction heater 31. Thereafter, the ceramiclid 35 is placed on top of the holding vessel 1 and fixed in position.Subsequently, air is blown from the cooling unit 37 against the outersurface of the holding vessel 1 for a specified period of time at aspecified timing, both being determined by a specific need, such thatthe molten metal M_(A) within the holding vessel 1 is cooled at anaverage rate of 0.01° C./s-3.0° C./s from the temperature right afterthe pouring of the melt until just before the start of the molding step,thereby generating fine primary crystals within the alloy solution; atthe same time, temperature adjustment is effected by means of theinduction heater 31 such that the temperatures of various parts of thesemisolid metal M_(B) in the holding vessel 1 will fall within thedesired molding temperature range for establishment of a specifiedfraction liquid not later than the start of the molding step. To enabletemperature control of the semisolid metal M_(B), the ceramic frame 34is so designed that it can be finely adjusted automatically to a desiredheight within the heating coil 31a. If it is not critical that thesemisolid metal M_(B) be maintained at a constant temperature beforemolding, there may be a case where the induction heater 31 need not beoperated.

When the semisolid metal M_(B) in the holding vessel 1 on the ceramicframe 34 has been held for a specified time at a specified fractionliquid, the cylinder 32 is lowered so that the holding vessel 1 is takenout of the induction heater 31, picked up by the transport robot 62 andimmediately inserted into the injection sleeve 200a which is of avertical type (or a horizontal type 200b) in the molding machine 200.

The term "a specified fraction liquid" means a relative proportion ofthe liquid phase which is suitable for pressure forming. Inhigh-pressure casting operations such as die casting and squeezecasting, the fraction liquid is less than 75%, preferably in the rangeof 40%-65%. If the fraction liquid is less than 40%, not only is itdifficult to recover the alloy from the holding vessel 1 but also theformability of the raw material is poor. If the fraction liquid exceeds75%, the raw material is so soft that it is not only difficult to handlebut also less likely to produce a homogeneous microstructure because themolten metal will entrap the surrounding air when it is inserted intothe sleeve for injection into a mold on a diecasting machine orsegregation develops in the metallographic structure of the casting. Forthese reasons, the fraction liquid for high-pressure casting operationsshould not be more than 75%, preferably not more than 65%. However, inthe case of alloys that have low shaping and flowing properties or toyield products that are difficult to shape, it is sometimes desirable toperform the shaping operation with a fraction liquid higher than 75%. Inthis case, a semisolid metal having a fraction liquid higher than 75%may be poured from the holding vessel into the sleeve.

In extruding and forging operations, the fraction liquid ranges from1.0% to 70%, preferably from 10% to 65%. Beyond 70%, an uneven structurecan potentially occur. Therefore, the fraction liquid should not behigher than 70%, preferably 65% or less. Below 1.0%, the resistance todeformation is unduly high; therefore, the fraction liquid should be atleast 1.0%. If extruding or forging operations are to be performed withan alloy having a fraction liquid of less than 40%, the alloy is firstadjusted to a fraction liquid of 40% and more before it is taken out ofthe holding vessel and thereafter the fraction liquid is lowered to lessthan 40%.

The robot 62 in the vessel transporting section 60 is a knownmulti-joint robot capable of three-dimensional movements. The robot maybe automated by means of a programmable personal computer or sequencerof a programmable controller.

According to the invention, semisolid metal forming will proceed by thefollowing specific procedure. In step (1) of the process shown in FIG.9, a complete liquid form of metal M is contained in the ladle 42a. Instep (2), the metal M is poured into the holding vessel 1 (which may bea ceramic-coated metallic vessel) as it is contacted by the inclinedcooling jig 70 [see step (I-a)], or with the melt being held superheatedto less than 50° C., preferably less than 30° C., above the liquidustemperature of the metal [see step (I-b)], or with the vibrating jig 52(specifically, vibrating rod 52A) being submerged in the melt to impartvibrations as it is progressively poured into the holding vessel 1 [seestep (I-c)]. As a result, there is obtained an alloy that containscrystal nuclei (or fine crystals) either just above or below theliquidus temperature of the metal.

In subsequent step (3), the alloy is cooled at an average rate of 0.01°C./s-3.0° C./s and held as such within the holding vessel 1 until justprior to the start of shaping under pressure so that fine primarycrystals are generated in said alloy solution; at the same time,temperature adjustment is effected with the induction heater 31 suchthat the temperatures of various parts of the alloy in the vessel 1 willfall within the desired molding temperature range (±5° C. of the desiredmolding temperature) for establishment of a specified fraction liquidnot later than the start of the molding step. In this case, a specifiedamount of electric current is applied before the representativetemperature of the metal slowly cooling in the holding vessel 1 from thetemperature right after the start of melt pouring has dropped to atleast 10° C. below the desired molding temperature and, hence, theinduction heater 31 needs to produce a comparatively small output power.For cooling the alloy, air is blown against the holding vessel 1 fromits outside. If necessary, both the top and bottom portions of theholding vessel 1 may be heat-retained with a heat insulator or heated sothat the alloy is held partially molten to generate fine spherical(non-dendritic) primary crystals from the introduced crystal nuclei [seestep (3-a) and (3-b)].

Metal M_(B) thus obtained at a specified fraction liquid is insertedfrom the inverted holding vessel 1 [see step (3-c)] into the injectionsleeve 200a of the molding machine (e.g. die casting machine) 200 andthereafter pressure formed within the mold cavity 208 on the moldingmachine to produce a shaped part. In order to ensure that the semisolidmetal M_(B) being discharged from the inverted vessel will not becontaminated by oxides, it is necessary that the surface portion of themetal which was situated in the top of the vessel 1 should face aplunger tip 210.

FIG. 10 is a cycle chart for the continuous semisolid shaping operation.To facilitate explanation, the chart assumes the use of a small numberof induction heaters which are each operated for 60 seconds. The generallayout of the production apparatus 100 is shown in FIG. 1. The specificoperating conditions were as follow.

(1) Induction heater: Three units (8 kHz, 10 kW)

(2) Holding vessel: One unit heating furnace (accommodating fivevessels)

(3) Molding cycle Sixty seconds

(4) Melt pouring and: Refiner (containing 0.15% Ti nucleating conditionsand 0.002% B); melt poured into holding vessel at 635° C.; See FIG. 5a.

(5) Time of holding metal: 150 seconds partially molten under aircooling and r-f induction heating

(6) Alloy: AC4CH (m.p. 615° C.)

The time course in each step of the semisolid shaping process is shownin FIG. 10 for each of the 8 holding vessels used. Obviously,casting isperformed at 60-sec intervals. FIG. 10 also shows the position of theholding vessel before and after the casting, as well as the operationsperformed at those times. The semisolid shaping metal produced by theprocess was shaped under pressure and a diagrammatic representation of amicrograph showing the metallographic structure of the shaped part isgiven in FIG. 11, from which one can see that the shaped part accordingto the invention has a fine structure which is by no means inferior tothat of the best semisolid shaped product ever known.

The obvious differences the invention process has from the conventionalthixocasting and rheocasting methods are clear from FIG. 9. In theinvention method, the dendritic primary crystals that have beengenerated within a temperature range of from the semisolid state are notground into spherical grains by mechanical or electromagnetic agitationas in the prior art but the large number of primary crystals that havebeen generated and grown from the introduced crystal nuclei with thedecreasing temperature in the range for the semisolid state arespheroidized continuously by the heat of the alloy itself (which mayoptionally be supplied with external heat and held at a desiredtemperature). In addition, the semisolid metal forming method of theinvention is characterized by the production of a uniform microstructureand temperature distribution by r-f induction heating with lower outputand it is a very convenient and economical process since it does notinvolve the step of partially melting billets by reheating in thethixo-casting process.

FIG. 12 is a plan view showing the general layout of an apparatus forproducing a semisolid shaping metal which is indicated by 101 and whichcomprises a crystal generating section 30 and a holding vesselconditioning section 10 which have rotating capabilities. The apparatus101 comprises the holding vessel conditioning section 10, the crystalgenerating section 30, a melt pouring section 40, a nucleating section50 and a vessel transporting section 60. A shaping apparatus indicatedby 200 in FIG. 12 is an example of the machine for shaping a semisolidmetal M_(B) produced with the apparatus 101 of the invention.

The holding vessel conditioning section 10 comprises a holding vesselcooling unit 11, an air blowing unit 16, a cleaning unit 12, a sprayunit 14 and a holding vessel rotating and transporting unit 17. Theholding vessel rotating and transporting unit 17 and the cleaning unit12 in the holding vessel conditioning section 10 are shown specificallyin FIG. 14. The holding vessel rotating and transporting unit 17 iscomposed of rotary actuators 17a and 17b and a vertically movingcylinder 17c. After inserting the semisolid metal M_(B) into theinjection sleeve 200a, water and air are successively injected into theholding vessel 1 by means of a device which, as shown in FIG. 3, has acylinder and a motor-driven vertically moving and rotating nozzle; thethus cooled and air-blown holding vessel 1 is transported by means ofthe unit 17 and lowered to rest on the receiveing stage 13 and fixed inposition. Thereafter, as shown in FIG. 2, the brush 12c is rotated toclean the inner surfaces of the holding vessel 1. After the brush 12c islowered, the unit 17 as it keeps retaining the holding vessel 1 israised and moved to the position of the spray unit 14. Thereafter, asshown in FIG. 3, a watersoluble coating containing a nonmetallicsubstance is injected from the spray unit 14 so that the inner surfacesof the holding vessel 1 are sprayed with the coating, and the appliedcoating is dried with air.

After the spray unit is lowered, the holding vessel 1 is moved to theposition of a holding vessel tilting or inverting device 18, where it isturned upside down and replaced within a holding vessel holder indicatedby 18a in FIG. 15. The holding vessel tilting or inverting device 18comprises an LM guide 18b, a linking rod 18c and a flexible joint 18d.The holding vessel holder 18a is allowed to tilt by means of the device18 in accordance with the pouring of the melt from the pouring ladle42a. The molten metal M₆ which contains Ti as the sole refiner and whichshould be held superheated to no more than 30° C. above the liquidustemperature of the metal is poured in using a holding vessel coolingaccelerating unit 19 as required. The molten metal M₆ poured into theholding vessel 1 is transported to the crystal generating section 30 bymeans of a robot 62. Thereafter, the molten metal M₆ is cooled down to ashaping temperature. The holding vessel cooling accelerating unit 19 maybe such that it injects air or water directly against the outer surfaceof the holding vessel or, alternatively, a chilling member may bebrought into contact with the holding vessel.

FIG. 13a is a plan view showing details of the crystal generatingsection of the apparatus shown in FIG. 12 for producing a semisolidshaping metal, and FIG. 13b is vertical section A--A of FIG. 13a. Asshown in FIGS. 13a and 13b, the crystal generating section 30 comprisesan induction apparatus 31 furnished with a heating coil 31a which isprovided around the holding vessel 1 for controlling the temperature ofthe metal in the holding vessel 1, a ceramic frame 34 that is capable ofheat-retaining or heating the holding vessel 1 and which is placed on avertically movable support table 33 for retaining or lifting out saidholding vessel 1 or replacing it by means of a secondary rotating shaft39a (i.e., replacement of a holding vessel of molten metal M_(A)containing crystal nuclei with a holding vessel of semisolid metal M_(B)which has been cooled to the shaping temperature) and for adjusting theposition of the holding vessel 1 within the heating coil 31a of theinduction apparatus 31, a vertically movable lid 35 that is capable ofheat-retaining or heating the top portion of the holding vessel 1 andwhich is furnished with a thermocouple 36 for measuring the temperatureof the metal in the holding vessel 1, a cooling unit 37 providedexterior to the heating coil 31a for injecting air of a specifiedtemperature against the outer surface of the holding vessel 1, aprotective cover 38 surrounding the above-mentioned components, and aprimary rotating shaft 39 on which four units of the crystal generatingsection can rotate or pivot.

When the holding vessel 1a of molten metal M_(A) containing crystalnuclei is placed on the ceramic frame 34 on the support table 33, theholding vessel 1b of semisolid metal M_(B) which has been adjusted tothe shaping temperature within the induction apparatus 31 is lowered bymeans of a vertically moving cylinder and then rotated by the secondaryrotating shaft 39a to be situated outside the crystal generating section30. At the same time, the holding vessel 1a of molten metal M_(A) israised by a vertically moving cylinder 32 to a specified position in theheating coil 31a of the induction apparatus 31, where the metal M_(A) iscooled to a specified temperature by means of the cooling unit 37 andits temperature is subsequently adjusted by the induction apparatus 31.Other units of the holding vessel 1 are subjected to the same sequenceof actions as described above. The holding vessel 1b of semisolid metalM_(B) which has thusly become situated outside the crystal generatingsection 30 is subsequently transported by the robot 62. Holding vessels1e/1f and 1g/1h which are situated far from the robot are pivoted(rotated through 90 degrees) by means of the primary rotating shaft 39to move to the positions of holding vessels 1c/1d and 1a/1b,respectively.

The function of the induction apparatus 31, as well as the conditionsfor cooling molten metal M_(A) in the apparatus 31 and the method ofcontrolling its temperature are essentially the same as outlined in FIG.8.

FIG. 16 is a plan view showing the general layout of an apparatus forproducing a semisolid shaping metal which is indicated by 102 and whichhas a moving crystal generating section 30 comprising a cooling zone 47and a temperature adjusting zone 48 having an induction apparatus 31.

The apparatus 102 comprises a holding vessel conditioning section 10,the crystal generating section 30, a melt pouring section 40, anucleating section 50 and a vessel transporting section 60. A shapingapparatus indicated by 200 in FIG. 16 is an example of the machine forshaping a semisolid metal M_(B) produced with the apparatus 102 of theinvention.

FIG. 17a is a plan view showing details of the crystal generatingsection of the apparatus shown in FIG. 16 and FIG. 17b is verticalsection B--B of FIG. 17a. The apparatus 102 is identical with what isshown in FIGS. 12 and 13, except for the crystal generating section.Therefore, only the crystal generating section 30 will be describedbelow in detail.

As shown in FIGS. 17a and 17b, the crystal generating section 30comprises a frame 34 capable of heat-retaining or heating the bottomportion of a holding vessel 1, a vertically movable lid 35 that iscapable of heat-retaining or heating the top portion of the holdingvessel 1 and which is furnished with a thermocouple 36 for measuring thetemperature of the metal in the holding vessel 1, a cooling zone 47comprising a cooling unit 37 which injects air or water of a specifiedtemperature, as required, against the outer surface of the holdingvessel 1, an automatic transport unit 49 for rotating the holding vessel1 at a constant speed, and a temperature adjusting zone 48 having aninduction apparatus 31 furnished with a heating coil 31a which isprovided around the holding vessel 1 for controlling the temperature ofthe metal in it.

Only after a holding vessel 1i is rotated by means of the automatictransport unit 49 to come to the position of a holding vessel 1m, theinduction apparatus 31 comes into action to adjust the temperature ofthe metal in the holding vessel 1. The apparatus 31 is either raised orlowered by a vertically moving cylinder 32 and stops in a specifiedposition where it surrounds the holding vessel 1.

FIG. 18 is a plan view showing the general layout of an apparatus whichis indicated by 103 and which has a stationary crystal generatingsection 30 comprising a cooling zone 47 and a temperature adjusting zone48 having an induction apparatus 31. FIG. 19a is a plan view showingdetails of the crystal generating section of the apparatus shown in FIG.18 for producing a semisolid shaping metal and FIG. 19b is verticalsection C--C of FIG. 19a. The crystal generating section 30 comprises aframe 34 capable of heat-retaining or heating the bottom portion of theholding vessel 1, a vertically movable lid 35 that is capable ofheat-retaining or heating the top portion of the holding vessel 1 andwhich is furnished with a thermocouple 36 for measuring the temperatureof the metal in the holding vessel 1, a cooling zone 47 comprising acooling unit 37 which injects air or water of a specified temperature,as required, against the outer surface of the holding vessel 1, and atemperature adjusting zone 48 having an induction apparatus 31 furnishedwith a heating coil 31a which is provided around the holding vessel 1for controlling the temperature of the metal in it. Unlike in the caseshown in FIGS. 16 and 17, the holding vessel 1 in the crystal generatingsection shown in FIG. 19 is of a stationary type and, therefore, theholding vessel 1 is transported by a robot 62 to thetemperature-adjusting zone 48 after it has been cooled to a specifiedtemperature by means of the cooling unit 37. Then, as in the case shownin FIG. 13, the holding vessel 1 is replaced on the ceramic frame 34 andthe temperature of the metal in it is adjusted by means of the inductionapparatus 31.

The criticality of the conditions for cooling the holding vessel in thestep of spheroidizing primary crystals in the process shown in FIG. 9may be explained as follows.

If the upper or lower portion of the holding vessel 1 is not heated orheat-retained while the alloy M_(B) poured into the vessel is cooled toestablish a fraction liquid suitable for molding, dendritic primarycrystals are generated in the skin of the alloy M_(B) in the top and/orbottom portion of the vessel or a solidified layer will grow to causenonuniformity in the temperature distribution of the metal in theholding vessel 1; as a result, even if r-f induction heating isperformed, the alloy having the specified fraction liquid cannot bedischarged from the inverted vessel 1 or the remaining solidified layerwithin the holding vessel 1 either introduces difficulty into thepractice of continued shaping operation or prevents the temperaturedistribution of the alloy from being improved in the desired way. Inorder to avoid these problems, if the poured metal is held in the vesselfor a comparatively short time until the molding temperature is reached,the top and/or bottom portion of the holding vessel is heated orheat-retained at a higher temperature than the middle portion in thecooling process; if necessary, both the top and bottom portions of theholding vessel 1 may be heated not only in the cooling process after themelt pouring but also before the pouring step.

If the holding vessel 1 is made of a material having a thermalconductivity of less than 1.0 kcal/mh° C., the cooling time is prolongedto a practically undesirable level; hence, the holding vessel 1 shouldhave a thermal conductivity of at least 1.0 kcal/mh° C. If the holdingvessel 1 is made of a metal, its surface is preferably coated with anonmetallic material (e.g. BN or graphite). The coating method may beeither mechanical or chemical or physical.

If the alloy M_(A) poured into the holding vessel 1 is cooled at anaverage rate faster than 3.0° C./s, it is not easy to permit thetemperatures of various parts of the alloy to fall within the desiredmolding temperature range for establishment of the specified fractionliquid even if induction heating is employed and, in addition, it isdifficult to generate spherical primary crystals. If, on the other hand,the average cooling rate is less than 0.01° C./s, the cooling time isprolonged to cause inconvenience in commercial production. Therefore,the average rate of cooling in the holding vessel 1 should rangepreferably from 0.01° C./s to 3.0° C./s, more preferably from 0.05° C./sto 1° C./s.

INDUSTRIAL APPLICABILITY

As will be understood from the foregoing description, the apparatus ofthe invention for producing semisolid shaping metals offers theadvantage that shaped parts having fine and spherical microstructurescan be mass-produced automatically and continuously in a convenient,easy and inexpensive manner without relying upon agitation by theconventional mechanical and electromagnetic methods.

What is claimed is:
 1. An apparatus for producing a semisolid shapingmetal that has fine primary crystals dispersed in the liquid phase andwhich also has a uniform temperature distribution, said apparatuscomprising:a melt pouring means comprising a melting furnace which meltsand holds a metal and a pouring device which lifts out the molten metalfrom said melting furnace, adjusts it to a specified temperature andpours it into a holding vessel; a nucleating means which generatescrystal nuclei in the melt as it is supplied from said pouring deviceinto said holding vessel; a crystal generating means which performstemperature adjustment such that the metal obtained from said nucleatingsection falls within a desired molding temperature range as it is cooledto a molding temperature at which it is partially solid, partiallyliquid; a holding vessel conditioning means which inverts the holdingvessel by turning it upside down so that a partially molten metal isdischarged and which then cleans the inner surfaces of the holdingvessel; and a vessel transporting means furnished with an automatingdevice including a robot with which the partially molten metal from saidnucleating means is transported into the injection sleeve of a moldingmachine.
 2. The apparatus according to claim 1, wherein the melt pouringmeans comprises:(1) a high-temperature melt holding furnace and alow-temperature melt holding furnace furnished with a pouring ladle; or(2) a pouring ladle furnished with a refiner feed unit and a temperaturecontrol cooling jig inserting device and a high-temperature melt holdingfurnace; or (3) a low-temperature melt holding furnace furnished with apouring ladle and a refiner-rich melt holding furnace also furnishedwith a pouring ladle; or (4) a pouring ladle furnished with a refinermelting radio-frequency induction heater and a low-temperature meltholding vessel; or (5) a low-temperature melt holding vessel furnishedwith a pouring ladle; and wherein the nucleating means is the holdingvessel.
 3. The apparatus according to claim 2, wherein the nucleatingmeans comprises either a holding vessel tilting or inverting unit bywhich the angle of inclination of the holding vessel can be variedfreely and automatically as required during and after pouring of themelt in accordance with its volume, or a holding vessel coolingaccelerating unit capable of cooling said holding vessel externallyduring and after pouring of the melt, or both of said holding vesseltilting or inverting unit and said holding vessel cooling acceleratingunit.
 4. The apparatus according to claim 1, wherein the melt pouringmeans is a low-temperature melt holding furnace furnished with a pouringladle and wherein the nucleating means comprises a vibrating jig and theholding vessel, said vibrating jig being capable of vertical movementand imparting vibrations to the melt as it is poured into said holdingvessel.
 5. The apparatus according to claim 1, wherein the melt pouringmeans is a melt holding furnace furnished with a pouring ladle andwherein the nucleating means comprises an inclining cooling jig and theholding vessel, said cooling jig being such that the angle ofinclination can be varied freely and automatically during and afterpouring of the melt in accordance with its volume.
 6. The apparatusaccording to claim 1, wherein the crystal generating means comprises:avertically movable frame on which the holding vessel is placed and whichis either furnished with a heating source for heating the bottom portionof said holding vessel or formed of an insulating material forheat-retaining said bottom portion; a vertically movable lid that iseither furnished with a heating source for heating the top portion ofsaid holding vessel or formed of an insulating material forheat-retaining said top portion and which is furnished with atemperature sensor for measuring the temperature of the metal in theholding vessel; and a cooling unit provided exterior to said holdingvessel for injecting air of a specified temperature against the outersurface of said holding vessel.
 7. The apparatus according to claim 6,wherein the crystal generating means comprises:a frame that is capableof heat-retaining or heating the bottom portion of the holding vesseland which is vertically movable for retaining or lifting out saidholding vessel and for adjusting its position within the heating coil ofthe induction apparatus; a vertically movable lid that is capable ofheat-retaining or heating the top portion of said holding vessel andwhich is furnished with a temperature sensor for measuring thetemperature of the metal in the holding vessel; an induction apparatusfurnished with a heating coil which is provided around the holdingvessel for controlling the temperature of the melt in the holdingvessel; and a cooling unit provided exterior to said heating coil forinjecting air of a specified temperature against the outer surface ofsaid holding vessel.
 8. The apparatus according to claim 6, wherein thecrystal generating means comprises:an induction apparatus furnished witha heating coil which is provided around the holding vessel forcontrolling the temperature of the metal in the holding vessel; a framethat is capable of heat-retaining or heating the bottom portion of theholding vessel and which is not only vertically movable but alsorotatable for retaining, lifting out or replacing said holding vesseland for adjusting its position within the heating coil of the inductionapparatus; a vertically movable lid that is capable of heat-retaining orheating the top portion of said holding vessel and which is furnishedwith a temperature sensor for measuring the temperature of the metal inthe holding vessel; and a cooling unit provided exterior to said heatingcoil for injecting air of a specified temperature against the outersurface of said holding vessel, and wherein the crystal generating meanscomprises a plurality of units which rotate or pivot about a singleaxis.
 9. The apparatus according to claim 6, wherein the crystalgenerating means comprises:a frame that is capable of heat-retaining orheating the bottom portion of the holding vessel; a vertically movablelid that is capable of heat-retaining or heating the top portion of saidholding vessel and which is furnished with a temperature sensor formeasuring the temperature of the metal in the holding vessel; a coolingzone comprising a cooling unit which injects air or water of a specifiedtemperature, as required, against the outer surface of said holdingvessel; and a temperature adjusting zone having an induction apparatusfurnished with a heating coil which is provided around said holdingvessel for controlling the temperature of the metal in said holdingvessel.
 10. The apparatus according to claim 9, wherein the crystalgenerating means further includes an automatic transport unit with whichthe holding vessel containing the metal cooled to a specifiedtemperature in the cooling zone is moved at a specified speed to thetemperature adjusting zone which is adapted to be such that either theheating coil of the induction apparatus or the holding vessel moves sothat the temperature of the metal in the holding vessel is controlledwithin the heating coil.
 11. The apparatus according to claim 9, whereinthe crystal generating means further includes a transport unitcomprising an automating device including a robot with which the holdingvessel containing the metal cooled to a specified temperature in thecooling zone is moved to the temperature adjusting zone which is adaptedto be such that either the heating coil of the induction apparatus orthe holding vessel moves so that the temperature of the metal in theholding vessel is controlled within the heating coil.
 12. The apparatusaccording to claim 1, wherein the holding vessel conditioning meanscomprises:at least two of the following three units, a holding vesselcooling unit that is capable of rotary and vertical movements and whichis also capable of injecting at least one of a gas, a liquid and a solidmaterial, an air blowing unit that is capable of rotary and verticalmovements and optional air injection, and a cleaning unit for cleaningthe inner surfaces of the holding vessel which has a brush that iscapable of rotary and vertical movements and air injection; a spray unitthat is capable of rotary and vertical movements and application of anonmetallic coating; and a holding vessel rotating and transporting unitwith which the holding vessel, with its opening facing down, can bemoved to and fixed on the top portion of each of said cooling unit, saidair blowing unit and said cleaning unit, and which is verticallymovable.
 13. The apparatus according to claim 1, wherein the holdingvessel conditioning means comprises a cleaning unit and a spray unit,said cleaning unit comprising a jig for cleaning the inner surfaces ofthe holding vessel which has a brush that is capable of rotary andvertical movements and air injection and a vertically movable jig forfixing the holding vessel, and said spray unit comprising a verticallymovable jig for applying a nonmetallic coating onto the inner surfacesof the holding vessel and a vertically movable jig for fixing theholding vessel.
 14. The apparatus according to claim 1, which furtherincludes a holding vessel heating means for adjusting the temperature ofthe holding vessel when it is empty.